DEVELOPMENT AND CHARACTERIZATION OF GENETIC RESOURCES FOR AGRONOMIC AND QUALITY TRAITS USING GENOMIC TOOLS
Location: Dale Bumpers National Rice Research Center
Title: Do rice varieties have differences in their plant mineral nutrition?
Submitted to: Extension Reports
Publication Type: Experiment Station
Publication Acceptance Date: December 5, 2011
Publication Date: December 9, 2011
Citation: Ratnaprapha, Pinson, S.R., Tarpley, L. 2011. Do rice varieties have differences in their plant mineral nutrition?. Extension Reports. November 2011 edition, pg 3-7. Viewed http://beaumont.tamu.edu/eLibrary/Newsletter/2011_Winter_Issue.pdf
As a first step, in 2007 and 2008, preliminary trials in both flooded and unflooded conditions were conducted on 1,643 rice varieties from more than 114 countries. These trials, conducted at the Texas AgriLife Research and Extension Center at Beaumont, identified differences in the mineral nutrition among rice varieties, with some having extreme grain mineral composition. In 2010, a study was conducted to determine the association between concentrations of minerals in grain with those seen in leaves of seedlings. One benefit is to determine if grain mineral differences can be selected by breeders in young seedlings (saving significant time compared with developing grain to then study). Another offshoot is the identification of varieties with seedlings that have exceptional ability to draw minerals from the soil and accumulate them in leaves. A positive association across varieties for a particular mineral would imply that screening studies could be conducted at the seedling stages, and desirable traits and their genes could be identified at this early growth stage. Forty rice varieties selected for their extreme grain mineral composition (as observed in the 2007 and 2008 trials) were grown in an outdoor potted plant study. Seven replications were grown, with a new replication planted each week. When the seventh replication was two weeks old, leaves were sampled from all replications to represent different plant growth stages. The tip (about 2-inches) of the most recent fully opened leaf per plant was sampled, and the concentrations of 16 mineral elements were determined using inductively coupled plasma-mass spectrometry (ICP-MS). Good associations were observed between the grain mineral concentrations obtained from the 2007-2008 field trials and seedling leaf mineral concentrations observed in the 2010 outdoor potted plant study for some minerals (molybdenum (Mo), calcium (Ca), arsenic (As), and cadmium (Cd)). That is, for certain minerals, many of the varieties that had high levels in the grain also had high levels in the leaves. In these cases, high leaf mineral concentration could be considered potentially predictive of high grain concentration. These associations also mean that the mechanisms controlling the concentrations and much of the plant nutrition specific for these minerals can likely be studied in seedlings. For many of the minerals, only some of the varieties that had high grain levels also had high leaf levels. Such variety-to-variety differences suggest that the different varieties have different mechanisms underlying their high grain concentrations. To answer the question presented in the title, rice varieties show clear differences in their mineral nutrition. An increased understanding of these differences can be exploited to improve rice grain mineral nutrition for humans, but also to improve rice plant mineral nutrition. For some minerals, research with seedlings can be used to accelerate breeding selections for improved grain and plant nutrition, and to identify physiological mechanisms controlling grain or plant mineral nutrient and anti-nutrient levels.